Help me build a decent gaming pc for my nephew. (Christmas Present)

[SanchoPanda]

Willing to spend around 800 dollars. He just got into pc gaming a few months ago. He's been playing league of legends and counter strike...

Help a breh out.

 

[Wiles]

System Build - PCPartPicker

 

[1970s HeRon Flow]

Damn $800 present for a nephew